Air displacement devices are used to increase the supply of air and fuel to internal combustion engines to boost engine horsepower. An example of an air displacement device is the “Roots blower” shown by P. H. Roots in U.S. Pat. No. 30,157 and G. Scheerer in U.S. Pat. No. 2,201,014. Each of these devices has a belt-driven shaft that drives two close-clearance rotors. The rotating rotors during each rotation sweep out a specific volume of air to an air receiver, such as an internal combustion engine. The rotational speed of the rotors largely determines the unthrottled volume of air discharged by the device to an air receiver.
C. N. Hansen and P. C. Cross in U.S. Pat. No. 6,241,498 disclose a supercharger having cooperating rotors drivably connected to an internal combustion engine for delivering an air/fuel mixture to the combustion chamber of the engine. The rotors have semi-cylindrical pockets and protrusions that continuously move air through the supercharger. The unthrottled volume of air delivered by the supercharger depends on the operating speed of the engine that drives the supercharger. The unthrottled volume of air delivered by the supercharger operating at a constant speed and pressure varies little. There are no air flow controls to regulate air flowing into and out of the supercharger.
C. N. Hansen and P. C. Cross in U.S. Pat. No. 8,539,769 disclose an internal combustion engine combined with a variable displacement supercharger operable to provide varying amounts of air to the engine that range selectively from below through above atmospheric pressures responsive to the power requirements of the engine. The supercharger has an air intake and male and female rotors rotated by the engine to move a mass of air from the air intake to the engine. The rotors are located within a housing having an air bypass opening and an air bypass passage in communication with an air passage for directing bypass air to the air intake of the supercharger. A slide assembly is movably mounted on the supercharger housing for movement toward the air intake of the supercharger to change the position of the slide assembly along the length of the rotor, the mass of air directed to the engine and the mass of air flowing back to the air inlet of the supercharger. The slide assembly changes the position of the air bypass opening whereby more of the rotor lengths are effective to increase the mass of air above atmospheric pressure that is directed to the engine. A throttle valve located in the air inlet of the supercharger regulates the air mass flowing into the supercharger below atmospheric pressure to control the power of the engine when boost is not required. A control processor is used to regulate the positions of the slide assembly and throttle valve according to the power requirement of the engine.
T. D. Blackwell in U.S. Pat. No. 4,281,975 discloses a screw compressor with male and female rotors and a slide valve mounted within a cylindrical bore that intersects with the bores accommodating the rotors. Air pressure exerted against the slide valve results in friction and wear between the slide valve and adjacent structures. A cylindrical bore accommodates the slide valve. Anti-friction structures comprising rollers rotatably mounted on the slide valve located in grooves in the side wall of the bore accommodating the slide valve. An alternative anti-friction structure comprises transversely extended arcuate grooves in the surface of a cylindrical bore and anti-friction balls located in the grooves in the bores and grooves in the slide valve.
L. S. Anderson in U.S. Pat. No. 6,227,834 discloses a screw compressor having male and female rotors and an adjustable slide for regulating gas discharge pressure and capacity. The slide has opposite sides having longitudinal grooves. Rollers mounted on the side wall of the bore accommodating the slide are located in the grooves of the slide to prevent the slide from being pressed into engagement with the rotors and to secure the slide against rotational movements. The supercharger of the invention has novel and advantageous structures and functions which increase the operating performance of an internal combustion engine.